Hello,
I have haproxy on a Intel® Xeon® CPU E5-2407 v2 @ 2.40GHz. It has one CPU with 4 cores.
The machine has two network interfaces eth0 and eth1 as bond0, active/passive. These are the interrupts stats:

What could I possibly doing wrong? What could be the problem? I’ve also tried with 4 processes pinned to CPU 0, 1, 2, 3 with a similar result. One process has most of connections compared to the other processes, and it’s always the lowest pid (first child forked I guess).

By default, the kernel wakes up all processes and they randomly pick the connections. Since kernel 3.9 the kernel queues incoming connections to each individual socket queue. But for this you need to add the “process” statement on your “bind” lines, which I’m pretty sure you don’t have